Electron beam lithography technology has been developed for the production of monolithic integrated circuits by means of writing an electron beam on an electron resist coated target wafer to expose selected areas of the wafer. Electrons are typically produced in such a system by thermionic emission and are formed into a beam by electrostatic and magnetic accelerating and focusing elements. The point of impact of the beam on the target is controlled by deflecting electrodes which bend the beam by means of electrostatic fields. In previous systems a single electron beam is produced which is sequentially directed to a plurality of discrete areas on the wafer.
A multielectron beam generation system is disclosed in U.S. Pat. No. 3,935,500 to Oess et al. In Oess each of the electron beams is generated and deflected in response to a modulating signal to produce a display on a phosphor screen. Each electron beam is generated by a cathode wire which is heated by current flow to produce electrons by thermionic emission.
Prior art electron generators have used an electron emissive wire electrode which is heated to the thermionic emission temperature by a heater element. However, electron beam generation in this manner does not produce a beam intensity sufficient for many applications. Further, such a structure does not lend itself to implementation as a multiple electron beam generator.
A need therefore exists for a multiple electron beam generator capable of producing intense small sources of electrons. A need also exists for an electron beam generator which can produce a source of electrons that are in a collimated beam which can be readily focused and deflected.